In a variable displacement vane pump, a cam ring swings using a pin as a fulcrum so as to vary an amount of eccentricity of the cam ring relative to a rotor, and as a result, a discharge volume of a working fluid is varied.
In a variable displacement vane pump disclosed in JP2005-337146A, first and second fluid pressure chambers are provided on an outer periphery of a cam ring, and the cam ring swings in accordance with a differential pressure between the first and second fluid pressure chambers.
A seal housing groove opposing the outer periphery of the cam ring is formed in an adapter ring that houses the cam ring, and a seal member is inserted into the seal housing groove. The seal member partitions the first and second fluid pressure chambers by coming into sliding contact with the outer periphery of the cam ring.
This type of seal member is constituted by a resin slipper seal that comes into sliding contact with the outer periphery of the cam ring, and a rubber elastic member that presses the slipper seal against the outer periphery of the cam ring.
Space is limited inside the variable displacement vane pump, and therefore the size of an opening cross-section (a groove depth) of the seal housing groove formed in the adapter ring is limited. Hence, the slipper seal is formed in a flat, thin plate shape having a rectangular cross-section so that space for inserting the elastic member is secured in the seal housing groove behind the slipper seal.